The present invention relates generally to downhole pump for subterranean wells and more particularly to fixed (conventional) hydraulic jet pump assemblies. More specifically this invention relates to a fixed jet pump having nozzle and throat which may be removed from the well without pulling the well tubing and having pressure sensors integrated into the pump assembly.
Hydraulic jet pumps have been a recognized and accepted tool for artificial lift in oil and gas wells for many years. When a well no longer has sufficient reservoir pressure to flow under its own power either to the surface or to flow to the surface at a satisfactory production rate, hydraulic pumping may be an option for lifting the fluid from the wellbore to the surface and through the surface facilities. Hydraulic pumping systems transmit stored potential energy contained in a pressurized source of power fluid to stored potential energy in produced fluids and ultimately to kinetic energy in produced fluids. The power fluid may be part of an open system and originate from the well, such as produced oil or produced water, or the power fluid may be confined to a closed loop system.
A popular hydraulic pump is the jet pump which operates by transferring the energy from a pressurized high velocity jet of power fluid directly to produced fluids drawn into the jet stream by a venturi effect created by the high velocity stream. Produced fluids are mixed with the power fluid and the mixture is lifted to the surface by the hydrostatic energy remaining in the mixture after mixing. Hydraulic jet pumps substantially involve no downhole moving parts. If the pressure drop on the produced fluid stream into the jet pump is sufficiently great, a suction may actually be created upon the face of the producing formation at the wellbore. Therefore, jet pumps may also be known as formation suction pumps.
Hydraulic jet pumps are dynamic pumps, as are electric submersible pumps and are to be distinguished from hydrostatic pumps such as reciprocating rod pumps. The objective in jet pumping is to create as much bottom hole pressure draw-down as possible in order to obtain maximum production rate. By altering the variable sizes of component parts, power fluid rate and pressure, jet pumps are capable of producing wells at produced fluid rates from less than 50 barrels of fluid per day (BFDP) to in excess of 10,000 BFPD. As such, in order to optimize system efficiency or resize pump components to adjust to changing well capabilities, it may be necessary to remove a pump rather frequently to make these adjustments. Cavitation, turbulence and friction may become excessive and result in operating inefficiencies in improperly designed jet pump systems, leading to excessive horsepower requirements and component wear. Depending upon the installation design, these problems may require pulling the power fluid tubing string from the well, and/or a production tubing string, and/or the jet pump assembly. In some installation designs the entire pump may be pumped to the surface by reversing flow of the produced and power fluid streams.
There are basically two distinct types of jet pumps. The first may be known as xe2x80x9cfixed pumpxe2x80x9d installations and the second may be known as xe2x80x9cfree pumpxe2x80x9d installations. In xe2x80x9cfixed pumpxe2x80x9d installations, the jet pump is run in the wellbore affixed to the power fluid tubing string. There are substantially two basic designs of fixed pump installations. In the first fixed pump installation, the jet pump is attached to the power fluid tubing string and the pump and power fluid tubing string are run inside of a larger tubing string, referred to as the production tubing string, and the pump is landed on a seating shoe which is attached near the bottom of the production tubing string. In this xe2x80x9cinsertxe2x80x9d type installation, power fluid may traverse down the inner power fluid tubing string, pass through the pump and the mixture of power fluid and produced fluid may be transmitted to the surface through the annulus between the two tubing strings. Alternatively, the fluid directions may be reversed. In this insert type, fixed jet pump installation, free gas may be vented up the annulus between the outer production tubing string and the casing. In addition, this installation may allow a larger diameter pump to be run in relatively small casing sizes. Power fluid strings in this installation may typically range in size from xc2xe inch to 1xc2xc inches, depending upon rate, pressure and production tubing size.
In the second fixed pump installation, the jet pump may be run in the wellbore on the power fluid tubing string and include a pack-off device, such as a packer, to seal between the power fluid tubing string and the well casing. Power fluid may typically travel down the power fluid tubing string, pass through the pump and return to the surface with the produced fluid, up the tubing/casing annulus. In this installation, produced gas must be handled by the pump. Therefore, this installation may typically be most applicable to well having low gas volumes and to wells having a relatively high production capacity.
In xe2x80x9cfree pumpxe2x80x9d installations, a relatively large tubing string may be run into a wellbore. A bottom hole assembly including a packer and standing valve may be run into the wellbore, concentrically through the larger tubing string, either on a smaller diameter, power fluid tubing string or on wireline. The packer may then be set in the annulus between the tubing strings and above the casing perforations. The xe2x80x9cfree pumpxe2x80x9d may then be circulated into the wellbore through the inner, power fluid tubing string and landed on the standing valve. Mixed power fluid and production fluid may then be produced to the surface through the annulus between the two tubing strings. The jet pump may be circulated out of the wellbore as desired to change or resize components in the pump by reversing the fluid directions, causing the standing valve ball to seat in the standing valve.
A free pump may also be retrieved by wireline operations. The free pump type casing installation may also be advantageous where production or power fluid may be transmitted through the wellbore casing, in that this installation only requires the purchase of one tubing string. A significant difference in the free pump casing installation and the fixed pump casing installation is that in the fixed pump casing installation the jet pump is attached to the power fluid tubing string and in the free pump installation the jet pump fits inside of the power fluid tubing string allowing the free pump to be circulated up and down the power fluid string.
In either the free pump installation or the fixed pump installation, the direction of flow for the power fluid and the mixed power and produced fluids may be in either direction such that the power fluid may be selectively transmitted down either the inner tubing string, or down the annulus between tubing strings or between the tubing casing annulus. However, internal components of the jet pump must be directionally oriented to properly accommodate the selected operating practice.
Technical references to jet pumps are known as far back as 1852, however, the first suggestion of an application to pumping oil wells, with a mathematical approach, was first disclosed in 1933. In 1864 Anger and Crocker were granted U.S. Pat. No. 44,587, on a jet pump. McMahon received six patents on oil well pumps beginning in 1930 with U.S. Pat. No. 1,799,483. Jet pumps began to achieve more accepted usage and with emphasized marketing in the oil patch in the 1970""s. U.S. Pat. No. T961,006 was granted to Brown in 1977, disclosing a method of controlling cavitation in jet pumps by high pump submergence below the producing formation, in a wellbore. A significant drawback to this invention is that it may require additional cost to drill, case and complete additional rat hole below the producing formation. In 1980, Roeder was granted U.S. Pat. No. 4,183,722, disclosing a jet pump including a conical deflector positioned in the axial center of the diffuser in order to effect more intimate contact of the power fluid with the produced fluid in order to increase the efficiency of the pump.
U.S. Pat. No. 4,237,976 was issued in 1980 to Wilson, disclosing a standard free pump type of jet pump installation. In the 976 patent, a packer is set above a producing interval on tubing and the tubing is perforated above a standing valve and landing nipple in the bottom hole assembly. A jet pump is pumped down the tubing and seated in the landing nipple while also sealing with the tubing above the perforation, such that power fluids may be pumped down the tubing and mixed power and produced fluids are transferred to the surface through the tubing/casing annulus.
In 1986, U.S. Pat. No. 4,603,735 was issued to Black, disclosing a conventional fixed pump insert type jet pump installation, as opposed to a fixed pump casing type installation. In the 735 patent, power fluid is pumped down the inner concentric tubing string, as done under prior art. This design differs from prior art in that the power fluid enters a venturi throat from below the venturi, as opposed to being accelerated through a jet nozzle, and accelerated fluid jet stream is discharged above the venturi. In addition, produced fluids are not drawn into the axial entrance to the venturi. Instead, produced fluids are drawn into the jet stream from a side port within the venturi throat.
In 1987, Black was issued another patent, U.S. Pat. No. 4,658,893, disclosing a variation to the previous fixed type insert pump installation. In the ""893 patent, the jet pump assembly, less the throat and nozzle, is run inside of the casing on a production tubing string, such as 2xe2x85x9c inch or 2xe2x85x9e inch. The throat and nozzle assembly is then run inside of the production tubing string on a smaller tubing string, such as a one inch string. The throat and nozzle are then inserted into the jet pump in an insertion conduit in the jet pump. Power fluid is then pumped down the smaller, inner string, through the pump and the mixed fluids are produced up the annulus between the two tubing strings.
In 1988, Weeks was granted U.S. Pat. No. 4,790,376, disclosing a fixed type insert pump which may be operated in convention circulation or in reverse circulation, such that in either installation the jet nozzle is oriented toward the surface. In 1992, U.S. Pat. No. 5,083,609 was granted to Coleman, disclosing modifications to concepts put forth in the ""893 patent granted previously to Black. Two balls were provided in the standing valve component of the ""609 patent as opposed to the single ball standing valve provided in the previous ""893 patent. Also, the ""609 pump is primarily a fixed type jet pump, in that it has a specially designed pump housing that must be run on the end of a tubing string, resulting in additional cost and complexity. The pump of the ""609 patent is also somewhat of a free pump in that a substantial portion of the pump assembly may be separately removed from the hole, as opposed to pulling merely the throat and nozzle as in the ""893 patent. The pump of the ""609 patent is also complicated and relatively inefficient due to the number of intricacies, port-holes and fluid passageways. The xe2x80x98pump of the 609 patent additionally also embodies the use of concentric tubing strings.
U.S. Pat. No. 5,372,190, also granted to Coleman, discloses a conventional type insert pump assembly which is a modification of the ""609 patent granted previously to Coleman, with the ""190 patent embodying differing structural details and operational characteristics. The jet pump of the ""190 patent is a conventional insert type jet pump, in that a pump housing is run in the wellbore on the end of tubing and embodies an inner concentric tubing string. The nozzle and throat may also be separately retrieved from the wellbore through the inner tubing string by reverse pumping or recovered on wireline.
An improved jet pump design is desired in order to improve mechanical system efficiency, simplify operational characteristics and provide the characteristic advantages of free pumps in a fixed pump installation. A simplified jet pump is desired which offers the ability to retrieve substantially all operational components of the jet pump assembly, including the standing valve assembly, while selectively operating the well in either operational direction and using the same pump components in either pumping direction. The disadvantages of prior art are overcome by the present invention and an improved jet pump installation is hereinafter disclosed.
A suitable embodiment of a jet pump assembly according to the present invention includes a fixed type jet pump installation having a retrievable insert assembly which may facilitate operation of the jet pump assembly in a normal circulation installation or in a reverse circulation installation. A simplified jet pump is provided which offers the ability to retrieve substantially all operational components of the jet pump assembly, including the standing valve assembly, without pulling either tubular conduit string, while selectively changing the direction of fluid circulation in the jet pump assembly and using the same pump components in either pumping direction.
A jet pump housing is provided which may be attached to the inner tubing string, similar to a fixed pump installation. In addition, a jet pump insert assembly is provided which includes substantially all of the working pump components, such that all of the insert assembly may be retrievable in one retrieving operation, by either wireline or by pumping the assembly from the housing, without pulling either tubular conduit from the wellbore.
It is an objective of the present invention to improve operational options with a given jet pump assembly. Connections are provided which permit key power section components to be directionally re-oriented and reconnected with the remaining pump components such that the insert assembly is operationally functional for pumping produced fluids either up the inner tubular conduit or up the annulus between the tubular conduits. This retrievability feature affords this invention desirable characteristics of free pump designs while also avoiding the problem of changing to different pump components or a completely different pump for changing the operational direction of fluid flow through the tubular conduits and through the jet pump.
It is also an objective of this invention to provide a simplified design, fixed type jet pump installation having retrievable components. When removed from the wellbore, the retrievable insert assembly of this invention recovers substantially all working components of the jet pump system which maybe subject to wear, resizing or operational modifications.
Another objective of this invention it to provide a jet pump assembly which may provide for pressure and temperature sensing and measuring equipment to be built into the recoverable insert assembly in the pump. The pressure and temperature measuring equipment may measure and record pressure and temperature of power fluid, produced fluid and mixed fluid streams, inside of the through bore in the jet pump assembly. Designed to be a permanent part of the installation, the pressure and temperature information may be selectively recorded and transmitted to the surface to monitor conditions at various selectable points in the jet pump assembly for optimizing the initial installation of the jet pump assembly. In addition, pressure and temperature conditions may be selectively polled at subsequent points in time in the life of the installation in order to monitor operating conditions and make operational adjustments in system performance.
It is a feature of the present invention to optimize system efficiency through analyzing pressure and/or temperature data from within the interior passages of the jet pump assembly in order to optimize system efficiency. Changes in power fluid pump rates and pressures, back-pressure regulator settings, and power fluid type may be monitored and changed during the life of the well as well production fluid characteristics change. Increases in gas-liquid ratios may be accounted for in optimizing power fluid rates. Changes in pump performance due to wear may also be directly measured by pressure and/or temperature recorders positioned at selected positions within the jet pump assembly.
It is also a feature of the present invention that the jet pump assembly may be cost effective to install and operate over the life of the installation. The retrievability feature provides for changing pump components without requiring pulling the tubing. Recording pressures and/or temperatures at various points in the jet pump facilitates fine tuning the jet pump assembly, both in initial operating characteristics, and as pump and well conditions change due to wear and well productivity changes.
These and further objects, features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawing.